Additive manufacturing has been in use for some time whereby objects are built up with small layers of various materials over time. Among others, methods of additive manufacturing include fused deposition modeling, selective laser sintering, and stereolithography to form these layers. All of these methods create an object by “slicing” the virtual object into layers that are then deposited one on top of the other until the final object is formed.
Typical methods for forming a structure include the addition of preformed objects together in sequence to form a larger building or other object. Buildings have been constructed using systems of materials that combine to form a composite assembly having many beneficial characteristics such as structural support, insulation, water resistance, and finished surfaces.
The conventional construction of objects or buildings involves materials that are cast, cut, machined, or extruded in various forms and are then combined together to form the final object or building. Many components are cut or customized in the field by removing material from the piece to fit it into the assembly. Within a typical building the shape of a beam or wall is calculated to resist its maximum load and then the entire beam or wall is of uniform shape and depth to account for the maximum load. This method of designing and constructing buildings has been in use since the first buildings were constructed. By contrast, in a natural system, material is at a premium and therefore the shape of an object is optimized for minimal use of the material. Current construction practice largely ignores nature's example. Building elements are designed for speed of manufacture and building erection; largely without consideration of material efficiency or flexibility of form. Customized shapes or structures are expensive and therefore rarely used in current construction practice.
Additive manufacturing techniques are currently in very limited use to produce large structures.
For instance, a toy used for freeform additive manufacturing uses plastic filament that is melted and pushed through a heated nozzle to extrude in open space. It is useful only as a toy without much control over the temperature, rate of extrusion, or feedstock material.
Metallic freeform sintering is also in use for a process called Direct Metal Deposition (DMD) whereby particles of metal are ejected from a nozzle while a high powered laser fuses the particles to the previously built up substrate while being controlled by a robotic arm.
One larger scale example involves use of brick-like modular plastic parts produced with a scaled up, layered Fused Deposition Modeling (FDM) approach. These units are then combined with other parts to form a larger building. Another method is adopts a similar approach with modular clay bricks that are 3D printed with an extruder mounted on a robotic arm.
At least two other methods utilize large gantry cranes to deposit material. One produces a building through layered deposition of cement with a gantry crane mechanism that is larger than the building being built. Another approach produces a large structure through the use of powdered stone material laid down in layers with a polymeric binder.
Another method attaches a plastic extruder to a robotic arm and is used to produce tension elements similar to cocoons or spider webs over a metal framework. Another similar effort uses a mechanism with a filament extruder on the end of a robotic armature to produce single material concrete walls where the mesh acts as ‘leaking formwork’ and the extrusions act as horizontal wall ties between the faces of the wall.
Existing 3D printing technology produces objects that are built up in a layered format through different means and materials, but are limited to small build volumes and a layer-wise buildup of material. Most examples exclusively use the 3D printed material to construct a structure and are constrained to the build volume of the printing mechanism employed.